Method and apparatus for producing tubes of vitreous materials



March 18, 1958 W. LERCH METHOD AND APPARATUS FOR PRODUCING TUBES OFVITREOUS MATERIALS Fild March 14, 1955 INVENT OR WALTER. LERCH '8; aw ik ATTORNEYS United States Patent METHOD AND APPARATUS FOR PRODUCINGTUBES OF VITREOUS MATEREALS Walter Lerch, Gelsenkirchen, Germany,assignor to Glasrmd Spiegel-Manufactur Act-Gen, Gelsenltirchen- Schalke,Germany, a corporation of Germany Application March 14, 1955, Serial No.4%,993

Claims priority, application Germany March 27, 19554 12 Claims. (Cl. 49--29) The present invention relates to improvements in a centrifugalcasting method for producing tubes of fused vitreous masses, such as,for example, glass, ceramics, slag, basalt, or other mineral substances,and to a new apparatus for carrying out such method.

Prior to this invention, several different methods have already beenproposed for applying and carrying out the centrifugal casting methodfor producing tubes of fused vitreous materials. Thus, for example, oneof these prior methods consisted in pouring the fused mass continuouslyinto a rotating vertical ingot mold provided with a bottom and in whicha molding core is rigidly mounted. The wall strength of the tube to beproduced by this method was determined by the width of the gap orclearance formed between the inner wall of the mold and the corethereof.

According to another prior method, the inner shape of the hollow body tobe produced, and thus the particular wall strength of such body, wasdetermined by inserting a rigid tool into the mold which was likewiseprovided with a bottom.

In other prior methods, while subjecting the fused mass to centrifugalforce, a plunger was moved upwardly from the bottom of a vertical moldso as to form the inner shape and determine the wall strength of thetube or hollow body.

All of these and similar centrifugal casting methods have inherentdisadvantages which render them impractical. It has also been found thatit is by no means possible simply to apply the well-known methods ofcasting metals by centrifugal force to molding fused, vitreousmaterials. Such a conversion ofthe known metal casting methods will notbe successful because of the difference in the chemical and physicalqualities of the two types of materials. While fused metallic masseshave within the range of their melting point a viscosity ofapproximately 2 to 5 centimeter-gram-second units, (C. G. S.-units),vitreous masses, for example silicate glasses, have within theirprocessing range a viscosity of to 10 C. G. S. units. Extensive researchand experiments by the present inven tor have shown that such lowfluidity of vitreous melts requires special operations and treatmentsfor filling the mold and for obtaining tubes of uniform wall strength.

While metallic melts flow easily into the mold and are uniformlydistributed when subjected to centrifugal force, vitreous melts actentirely different since they flow very slowly and easily stick to thefeed channel. A very great disadvantage of vitreous melts as comparedwith metallic melts also resides in the fact that the vitreous melt willnot flow from the end of the feed channel into the mold but due to itsviscosity will form a thread which, when the mold is being rotated,winds into a spiral shape, so that when these spirals then overlap eachother, considerable amounts of air will be enclosed between them.

All prior proposals to remedy this disadvantage, such as pouring themelt with a ladle into a vertical mold, or inserting cores and othertools, did not lead to any satisfactory results since the wall strengthof the tubular or "ice other hollow bodies thus produced could never bemade uniform.

Also, the difficult application of different molding cores, tools, orplungers for determining the wall strength of such tubular bodiesrenders such methods unduly complicated, especially since it requiresseparate operations for inserting and removing such tools or cores.

The worst difliculties of these prior methods, in'which a mold with asolid bottom was used, however, consisted in the removal of the moldedsolidified objects from such a mold. This difiiculty was aggravated bythe absolute requirement that glasslike products, and particularly thosemade of melts containing silicate, must, after being molded, be veryquicky removed from the mod so asto avoid crystallization of thesematerials which would lead to excessive tensions in the product andbreakage thereof.

In order to overcome these disadvantages, it has also been proposed todesign the mold so as to be pivotable about a horizontal axis. However,even this proposal did not lead to any satisfactory results since by thecentrifugal force of the molding operation, the material is forcedtightly against the inner wall of the mold and the solidified productwill thus cling to the wall of the mold and will not simply side out ofthe mold even though the latter is pivoted, or even placed upside down.Also, the machinery required for pivoting the heavy molds rendered theentire mcehanism very expensive.

It is the primary object of the present invention to provide a newmethod of producing tubes of fused vitreous materials by the applicationof centrifugal force, a method which is superior to all those knownprior to thisinvention and which by the application of very simple andeffective means overcomes all their disadvantages as outlined above.

The principal features of the invention for carrying out this'objectconsist in the use of a rotatable mold which is preferably slightlyinclined to the horizontal; in feeding the melt intermittently and dropby drop into the mold; and, while thus feeding the melt, insuccessively, although preferably intermittently moving the mold awayfrom the inlet point of the melt, or in depositing the meltintermittently side by side within the mold.

The new method of feeding the melt drop by drop into the mold has theconsiderable advantage over prior methods that the vitreous mass may befed at a much higher speed than when it is fed in a continuous stream,since the individual drop or slug will hardly cool off while beinginserted into the mold.

The first drop or slug will then pass to the end of the mold directlyopposite to the place of insertion, and the rotation of the mold willshape this drop into a ring. Shortly, thereafter, the second dropfollows and, by the lateral travel of the mold, it will be depositednext to the first ring and form a second ring which through thecentrifugal force fuses together with the first ring so as to form asingle unit. This continues until the mold will be filled entirely.Although not absolutely necessary, such depositing of the successiveslugs of molten material and the fusion of one ring of material to thepreceding ring may be facilitated by slightly inclining the entire moldso that the molten material has the natural tendency to slide toward thepreceding ring to combine therewith.

Another object of the present invention consists in producing tubes ofglass or similar materials which are free of enclosed air.

This object is likewise attained by the new method of feeding thevitreous mass drop by drop which thus avoids the disadvantage of priormethods of forming spiral threads which, when superimposed upon eachother enclose considerable amounts of air intermediate the differentthreadlike layers.

Another important feature of the invention resides in the end surfacesof the final product.

the use of a rotatable mold which is open at both ends and thus permitsthe solidified product to be easily and quickly removed therefrom.

Another feature of the invention consists in the use of removable ringswhich are adapted to be placed upon the twoends of the mold and projectradially inwardly of the inner edge of the mold, and determine the wallstrength of the tubes to be formed.

Thus, as soon as the molded body has cooled off sufficiently, the tworings are removed from the open ends of the mold, permitting the moldedbody to be ejected quickly and without difficulty from the mold by meansof a suitable ejecting tool placed upon the one free end of the body.

According to another feature of the invention, the end rings of the moldare preferably designed so as to be pivotablerrelative to the mold.Furthermore, in order to facilitate, the ejecting operation, it isanother feature of the invention to make the inner wall of the moldslightly conical, but of a degree which does not affect the wall Istrength of the tubes to any appreciable extent.

The present invention also has the important advantage that all the,complicated means for removing the molded article from the mold,required by previous methods, such as, for example, mechanisms forpivoting the entire mold, will be unnecessary.

The experiments and tests carried out by the present inventor have alsoshown that considerable advantages are obtained if the mold itself, andpossibly also the mass to be molded or While being molded, be heatedbefore,

during, and after the molding operation or at one ,or

another of these times, and if the central part of the mold i also becooled at such time. mold will, as a matter of course, cool offrelatively quickly as compared with the central part of the mold. Suchuneven cooling of the molded article may, however, cause Ordinarily, theendsof the i radially inward of the open ends of the mold, and whichduring the rotation thereof form the front and rear end surfaces of themolded article, with profiled portions in accordance with the desiredshape or cross section of If tubes are, for example, to be cast whichare to be used for conduits,

V one of the rings is preferably given the profile of a groove and theother that of a corresponding tongue. The individual tubes thus cast inthe mold will then have the respective opposite profiles and may beeasily fitted together with the tongue at the end of one tube fittinginto the groove in the end of the adjacent tube.

In order to assure an even and firm placement of the ejecting tool uponthe respective end i of the molded article when removing the same fromthe mold, it is also desirable that such tool be given a suitable endprofile corresponding to that of the respective end of the article to beejected.

Further objects, features, and advantages of the present invention willbe apparent from the following detailed description of the inventionwhen regarded with reference to the accompanying diagrammaticaldrawings, in which Fig. 1 shows a side view, partly in section, of amold according to the invention which is rotatably supported on acarriage; while Fig. 2 shows a top view of two molds according to theReferring particularly to the drawings, the mold 1 is of the inventionand may consist of various ditferent means known for similar purposes.

According to the present invention and as diagrammatically illustratedin Fig. 1, the fused vitreous mass is fed into the mold 1 through thefeed channel 7 intermittently and in the form of individual dropsorslugs A. For throwing the slug A so as to pass along its trajectoryfar into the interior of the mold 1, the lower end of the channel 7 ismade horizontal or even slightly upwardly inclined. For limiting theextent of the trajectory, a stationary deflector 8 is inserted into theopen outer end of mold 1 by moving the mold relative thereto. As soon asthe first slug A has dropped upon the inner wall of mold 1 at the outerend thereof and has by the rotation of the mold 1 been spun into a ring,the mold 1 together, with its driving means will be shifted slightly inthe direction shownby the arrow by means of a winch 9 which ispreferably driven by a suitable motor. Thus, deflector 8 then extendingslightly deeper into the mold, the next slug A will be droppedimmediately adjacent the first ring of fused material. Since thesuccessive slugs follow each other very quickly, the ring of fusedmaterial formed on the inner wall still retains such a high temperaturethat the newly formed ring fuses together with the first ring into ahomogeneous unit. These steps of slightly advancing the mold 1, throwinga new slug A of molten material into mold 1 against the deflector 8 soas to drop immediately adjacent the ring of molten material previouslyformed, and forming the next ring and fusing the same to theprecedingring are then continued in quick succession until the entiretube B is formed along the inner wall of mold 1.

For predetermining the wall strength of the tube B, ring-shaped members10 and 11 are secured to the two ends of the mold so as to be easilyremoved therefrom. These ring-shaped end portions 10 and 11 are made ofsmaller inner diameter than the inner wall of mold 1 so as to forminwardly projecting flangs 10a and 11a.

The amount of molten material to be fed into the mold 1 in the form ofdrops or slugs A may be predetermined for each particular tube to becast by means known as such so that the area bordered by the wall of themold 1 and the flanges 10a and 11a will just be filled out. As soon asthe molten mass has solidified, rings 10 and 11 will be removed,permitting the completed tube to be easily ejected from one open end ofthe mold 1 by means of a suitable tool placed upon the opposite end ofthe tube B.

In order to expedite the ejection of the tube B so that it may be pushedout as soon as the material has solidified,

the ring shaped members 10 and 11 are provided with suitable means whichpermit them to be quickly dis connected and removed from the outer endsof mold 1. Preferably, the rings 10 and 11 are for this purpose suitablymounted so as to permit them to be pivoted relative to the ends ofmold 1. In connection with such pivoting means, suitable quick-actinglocking means may A the same are then subjected to a slow coolingprocess as customary with silicate products.

Further, according to the invention as illustrated in Fig. 1, theflanges a and 11a which are projecting inwardly of the outer wall of themold 1 may be provided with suitable annular projections or recesseswhich may be desired for the subsequent use of the tubes pro duced inthe mold. Thus, for example, the flange 10a of the ring 10 may beprovided with an annular groove 10d of any suitable cross-sectionalshape, while flange 11a on the other ring 11 may be provided with acorresponding annular projection or tongue lid. When centrifugallycasting tubes in the mold 1, the molten mass automatically flows orpresses into the annular crevices formed by the groove 10d and theprojection or tongue 11d, leaving an accurate negative imprint thereofon the respective end surface of the tube B, so that each tube whensolidified has a corresponding annular tongue and groove at its outerends, permitting a series of such tubes to be fitted together to form acontinuous conduit, the tongue and groove of adjacent tubes theninterengaging with each other so as to form a tight seal.

The provision of such tongue or groove on the respective ends of thetube has the further advantage that the ejecting tool may be moreaccurately applied to the respective end of the tube for ejecting thesame after the material has solidified. Such ejecting tool is thenpreferably provided with an end surface corresponding to the shape ofthe respective end of the tube, that is, either with a recessed portionto fit over the tongue 10d of the finished tube B- or a projectingportion to fit into the groove 11d, depending upon the direction fromwhich the ejecting tool is applied upon tube B. Thus, a damage of therespective end of the tube B by the application of the ejecting tube maybe more safely avoided.

In the practical operation of the new centrifugal casting mold it hasbeen found desirable to provide two such molds in a tandem arrangement,as illustrated, for example, in Fig. 2. Such arrangement permits thecasting operation to be carried out continuously and especially theoperation of the mechanism which produces the individual drops or slugsof molten vitreous material and feeds the same intermittently, althoughin quick succession through the channel 7 either to the drum 1 or thedrum 1a. These two drums are preferably of identical size and shape andare each mounted together with their own driving mechanism 4 or 4a on aseparate carriage 6 or 611, respectively, in opposite positions to eachother. Separate Winches 9 and 9a draw the carriages 6 and 6a along aslightly upwardly inclined track in the direction toward the right asshown by the arrow and in the manner as previously described, so as toadvance the respective mold relative to the stationary deflector 8. Asuitable mechanism may also be provided as diagrammatically indicated inFig. 2, to shift the deflector 8 as well as the feed channel 7 from onemold to the other. The entire operation of the tandem arrangement,including the shifting of the deflector 8 and the feed channel 7 fromone mold to the other, may be controlled automatically so that one moldwill always be rotated and filled with molten material, while the rings10 and 11 are removed or pivoted away from the ends of the other mold,the completed tube is ejected therefrom, the rings 10 and 11 are againplaced on the ends of the mold, and the latter is returned toward theleft to its starting position to be newly filled during the nextoperating cycle.

Obviously, instead of mounting the entire mold 1 including'its drivingmechanism 4 on a moveable support or carriage 6 and moving such carriagerelative to a stationary deflector 8 so as to deposit the slugs ofmolten material successively but intermittently adjacent the precedingring of molten material, the arrangement may also 6 be made to mount themolds including their driving means in a stationary position, and toprovide suitable means for shifting the deflector 8 intermittentlytoward and into the respective open end of the mold.

While I have described my invention with reference to the preferredembodiments thereof I wish to have it understood that it is in no waylimited to the details of such embodiments or to the specific examplesdescribed, but is capable of numerous modifications within the scope ofthe appended claims.

Having thus fully disclosed my invention, what I claim is:

1. Method for the centrifugal casting of tubes from viscous melts, whichcomprises intermittently progressively depositing individual slugs of aviscous melt on the inner wall of a rotating centrifugal mold at pointslocated within adjacent planes extending at right angles to the moldaxis, whereby the individually deposited slugs are formed by therotation of the mold into rings which are fused together forming a tubein the mold, and recovering the formed tube from the mold aftersolidification thereof.

2. Method according to claim 1, in which said rotating centrifugal moldis maintained with its axis slightly inciined to the horizontal.

3. Method according to claim 1, in which said depositing is effected byfeeding individual slugs of the melt to the mold and throwing the slugsinto the mold along a trajectory terminating at said points.

4. Method according to claim 1, which includes heating the mold near itsends.

' 5. Method according to claim 1, which includes cooling the centralportion of the mold after the formation of said tube.

6. Apparatus for centrifugally casting tubes from viscous melts,comprising a rotatable mold, means for depositing individual slugs of aviscous melt upon the inner wall of said mold at points located withinadjacent planes extending at right angles to the axis of rotation ofsaid mold and progressively from one end of the inner wall of said moldto the other, and means for rotating said mold.

7. Apparatus according to claim 6, in which said mold has its axis ofrotation slightly inclined from the horizontal.

8. Apparatus according to claim 6, in which said mold is an open-endedmold having annular flanges removably secured to its ends.

9. Apparatus according to claim 6, in which said mold has at least oneopen end, and in which said means for depositing said slugs includes achannel extending into the open end of said mold and curved slightlyupwardly.

10. Apparatus according to claim 9, including a deflector extending intosaid mold and positioned within the trajectory path of slugs passingthrough said channel to deflect said slugs upon the inner wall of saidmold, and including means for producing a relative movement between saiddeflector and said mold, so as to move said deflector from one end ofsaid mold toward the opposite end thereof for depositing said slugsuniformly along the length of said wall.

11. Apparatus according to claim 10, in which said mold is an open-endedmold having annular flanges removably secured to its ends and mountedwith its axis of rotation slightly inclined to the horizontal, saiddeflector being a fixed deflector extending to the opposite end of saidmold, and including means for progressively moving said mold withrespect to said deflector.

12. Apparatus according to claim 11, in which said mold is mounted on a'carriage and in which said means for moving said mold relative to saiddeflector are means for moving said carriage.

(References on following page) 7 References Cited in the file of thispatent UNITED STATES PATENTS Millsbaugh -1 Apr. 8, 1913 Thompson May 10,1921 5 Hall Nov. 24, 1925 French Feb. 15, 1938 Engels June 21, 1938 8FOREIGN PATENTS France Dec. 9, 1927 Great Britain Nov. 19, 1931 GreatBritain July 24, 1937

